At present there is a trend of increasing drugs containing Biologically Active Substances (BAS) of the plant origin in their composition. Standardization of the medicinal plant raw material and development of methods of quality control for multi-component drugs of the plant origin are one of the topical problems of modern pharmaceutical science. The work in development of methods of the quality control for biologically active substances of the complex herbal extract in the composition of “Cholophyt” syrup has been conducted in order to create the corresponding sections of the analytical normative documentation for the drug. The presence of the amount of hydroxycinnamic acids, being similar with the reference sample by the structure, has been proven in the herbal extract and in the syrup by the methods of absorption spectrophotometry and thin-layer chromatography compared to the reference standard of chlorogenic acid. The quantitative content of BAS was studied in the dosage form under research by the method of absorption spectrophotometry in the ultraviolet and visible region in 20% solution of ethanol at the wavelength of 237 nm. The content of the amount of hydroxycinnamic acids was calculated by the method of standard and specific absorbance calculated with reference to chlorogenic acid. According to the results of studying the validation characteristics it has been found that the method for quantitative determination of the amount of hydroxycinnamic acids in the syrup calculated with reference to chlorogenic acid is accurate, precise and linear ( Z Δ =1.02 ≤max Z Δ =1.60, ïÂÂ¤=0.47≤max ïÂÂ¤=0.51, a=|0.695| ≤ max a=2.60, r=|0.9999| ≥ min r=|0.9981|).